Physical Chemistry and Transition Elements | OCR A-Level Chemistry A (H432)
Physical Chemistry and Transition Elements
- 101 questions
- 7 subtopics
- Module 5: Physical chemistry and transition elements
- Component 01 and Component 03
The quantitative treatment of equilibrium with Kc and Kp, lattice enthalpy through the Born-Haber cycle and the enthalpies of solution and hydration, and entropy and Gibbs free energy as the test of whether a reaction is feasible..
It covers mole fraction, partial pressure and ICE tables, kc and Kp expressions, their units and calculations, what changes the equilibrium constant, and the reaction quotient, lattice enthalpy and the Born-Haber cycle, enthalpy of solution and hydration, and the effect of ionic charge and size, entropy and calculating entropy change and gibbs free energy and thermodynamic feasibility.
Sample questions from Physical Chemistry and Transition Elements
Answer each one closed book first, then open the answer.
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Mole fraction, partial pressure and ICE tables
State the relationship between partial pressure, mole fraction, and total pressure.
Show the answer
Partial pressure equals mole fraction multiplied by total pressure: pₐ = xₐ × P_total. -
Mole fraction, partial pressure and ICE tables
How are equilibrium moles determined in an ICE table calculation?
Show the answer
Calculate equilibrium moles by adding the initial amounts and the changes for each species. -
Kc and Kp expressions, their units and calculations
Why are solids and pure liquids omitted from Kc and Kp expressions in heterogeneous equilibria?
Show the answer
Because their concentrations are constant and do not affect the equilibrium expression. -
Kc and Kp expressions, their units and calculations
After writing the balanced equation, what must be written next when calculating Kc?
Show the answer
Write the Kc expression with products over reactants, each raised to their stoichiometric coefficients. -
What changes the equilibrium constant, and the reaction quotient
Does adding a catalyst change the value of the equilibrium constant?
Show the answer
No, the equilibrium constant is unaffected by the presence of a catalyst. -
What changes the equilibrium constant, and the reaction quotient
Explain why changing temperature causes both K and the equilibrium position to change.
Show the answer
When temperature changes, K changes to a new value, and the position of equilibrium shifts to establish concentrations or partial pressures that satisfy the new equilibrium constant. -
Lattice enthalpy and the Born-Haber cycle
Which enthalpy term in a Born-Haber cycle represents the overall energy change for forming the compound from its elements?
Show the answer
The enthalpy of formation of the compound. -
Lattice enthalpy and the Born-Haber cycle
Where does lattice enthalpy appear in a Born-Haber cycle?
Show the answer
As the enthalpy change for forming the ionic lattice from its gaseous ions, completing the cycle.
The 7 subtopics
One subtopic is one session. Work down the list.
| Subtopic | What it covers | Questions |
|---|---|---|
| Mole fraction, partial pressure and ICE tables | Recall questions on mole fraction and partial pressure, Dalton's law, and using an ICE table to reach the equilibrium amounts. | 14 |
| Kc and Kp expressions, their units and calculations | Recall questions on writing each expression, homogeneous against heterogeneous equilibria, why solids and pure liquids are omitted, and deriving the units. | 15 |
| What changes the equilibrium constant, and the reaction quotient | Recall questions on why only temperature changes K, what concentration, pressure and a catalyst do instead, and predicting the shift from Q against K. | 17 |
| Lattice enthalpy and the Born-Haber cycle | Recall questions on the definition and sign of lattice enthalpy, the atomisation, ionisation and electron affinity terms, and the relationship around the cycle. | 19 |
| Enthalpy of solution and hydration, and the effect of ionic charge and size | Recall questions on the three linked terms, why dissolving can be endothermic, and how ionic charge and radius affect both lattice and hydration enthalpies. | 13 |
| Entropy and calculating entropy change | Recall questions on what entropy measures, the order of the three states, what a change in the number of gas molecules does, and calculating ΔS from standard entropies. | 12 |
| Gibbs free energy and thermodynamic feasibility | Recall questions on ΔG = ΔH − TΔS, the condition for feasibility, and why a negative ΔG does not guarantee that a reaction is observed. | 11 |
How the guide is worked
Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.
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Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
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Step 2 · Open book
Go back to the top. Read each printed answer and write it out in full, including the ones you had right.
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Step 3 · Closed book again
Same questions, same order, from memory. The gap between pass one and pass three is the session result.
Read the full method, the return schedule and the research behind it.
Nearby sections
OCR A-Level Chemistry A Active Recall Guide
Every section, not just this one. 1,913 questions with their answers.